In recent years, indium gallium zinc oxide (IGZO), which is one type of transparent amorphous oxide semiconductors (TAOS), has attracted attention because of its high electrical conductivity, and has been discussed to be used as a material for forming a thin film transistor (TFT) to be used in an active matrix liquid crystal display device or an OLED display device.
Japanese Patent Application Laid-open No. 2010-263064 discloses a method of manufacturing a thin film transistor as follows. A light-shielding gate electrode is formed on a TFT semiconductor layer formed of IGZO through intermediation of a gate insulating film. The semiconductor layer is irradiated with ultraviolet rays from the gate electrode side, to thereby form amorphous source and drain regions having a higher conductivity than that before irradiation.
In the manufacture of the liquid crystal display device, if the structure of the TFT can be simplified, advantageous effects can be expected, such as reduction in manufacturing cost, and improvement in aperture ratio or increase in pixel resolution due to reduction in size of a TFT occupying region.
This application has been made by focusing on the property of IGZO or a material similar thereto, and has an object to simplify the structure of the TFT to be used in the liquid crystal display device.